Study on Dynamic Interfacial Tension of 3‐Dodecyloxy‐2‐hydroxypropyl Trimethyl Ammonium Chloride at n‐Decane/Water Interface

Abstract

Dynamic interfacial tension (DIT) and interface adsorption kinetics at the n‐decane/water interface of 3‐dodecyloxy‐2‐hydroxypropyl trimethyl ammonium chloride (R12TAC) were measured using spinning drop method. The effects of RnTAC concentration and temperature on DIT have been investigated, the reason of the change of DIT with time has been discussed. The effective diffusion coefficient, D a, and the adsorption barrier, ϵa, have been obtained with extended Word‐Tordai equation. The results show that the higher the concentration of surfactants is, and the smaller will be the DIT and the lower will be the curve of the DIT, and the R12TAC solutions follow a mixed diffusion‐activation adsorption mechanism in this investigation. With increase of concentration in bulk solution of R12TAC from 8×10−4 mol · dm−3 to 4×10−3 mol · dm−3, D a decreases from 2.02×10−10 m−2 · s−1 to 1.4×10−11 m−2 · s−1 and ϵ a increases from 2.60 kJ · mol−1 to 9.32 kJ · mol−1, while with increase of temperature from 30°C to 50°C, D a increases from 2.02×10−10 m−2 · s−1 to 5.86×10−10 m−2 · s−1 and εa decreases from 2.60 kJ · mol−1 to 0.73 kJ · mol−1. This indicates that the diffusion tendency becomes weak with increase strength of the interaction between surfactant molecules and that the thermo‐motion of molecules favors interface adsorption.